Feedback calibration of digital to time converter

Abstract

This document discusses apparatus and methods for compensating non-linearity of digital-to-time converters (DTCs). In an example, a wireless device can include a digital-to-time converter (DTC) configured to receive a phase data information from a baseband processor and to provide a first modulation signal for generating a wireless signal, a detector configure to receive the first modulation signal and provide an indication of nonlinearities of the DTC, and a pre-distortion module configured to provide pre-distortion information to the DTC using the indication of nonlinearities.

What is claimed is: 
     
       1. A wireless device comprising:
 a digital-to-time converter (DTC) configured to receive a phase data information and to generate a first modulation signal for a wireless signal; 
 a detector configure to receive the first modulation signal and to determine an indication of nonlinearities of the DTC; and 
 a pre-distortion module configured to generate pre-distortion information for the DTC using the indication of nonlinearities. 
 
     
     
       2. The wireless device of  claim 1 , wherein the detector includes a time-to-digital converter (TDC) configured to receive the phase data information, to measure phase differences between each phase modulation word of the phase data information and the first modulation signal, and to determine the indication of nonlinearities using the phase differences. 
     
     
       3. The wireless device of  claim 2 , wherein the TDC includes a stochastic-beating TDC. 
     
     
       4. The wireless device of  claim 3 , wherein the stochastic-beating TDC includes:
 a beating TDC configured to generate course resolution; and 
 a stochastic TDC configured to generate fine resolution. 
 
     
     
       5. The wireless device of  claim 4 , wherein the stochastic-beating TDC includes:
 a flip-flop network; and 
 a triggered ringing oscillator (TRO); 
 wherein an output of the TRO is configured to sample the phase data information and the flip-flop network is configured to sample and hold an edge of an output of the DTC. 
 
     
     
       6. The wireless device of  claim 1 , wherein the detector includes a statistical extractor, the statistical extractor configured to statistically measure the first modulation signal and to compare the statistical measurement of the first modulation signal to a known statistical measurement of the phase data information. 
     
     
       7. The wireless device of  claim 6 , wherein the pre-distortion module includes a noise shaper; and
 wherein the detector is configured to adjust parameters of the noise shaper to compensate for nonlinearities of the DTC using the comparison of the statistical measurement of the first modulation signal to the known statistical measurement of the phase data information. 
 
     
     
       8. The wireless device of  claim 6 , wherein the detector is configured to generate a pre-distortion mapping table; and
 wherein the a pre-distortion module is configure to compensate for nonlinearities of the DIV using the pre-distortion mapping table. 
 
     
     
       9. The wireless device of  claim 6 , wherein the statistical extractor includes a time-to-digital converter (TDC) configure to provide a histogram of the first modulation signal. 
     
     
       10. The wireless device of  claim 9 , wherein the statistical extractor is configured to interpolate the histogram if the resolution of the DTC differs from the resolution of the TDC. 
     
     
       11. The wireless de-vice of  claim 9 , wherein. the TDC includes a stochastic-beating TDC. 
     
     
       12. A method of compensating nonlinearities of a transmitter, the method comprising:
 receiving a phase data information at a DTC of the transmitter; 
 generating a phase modulation signal using the DTC and the phase data information; 
 receiving the phase modulation signal at a detector; 
 determining an indication of nonlinearities of the DTC using the detector, the phase modulation signal and the phase data; and 
 generating pre-distortion information for the DTC using the indication of nonlinearities and a pre-distortion module. 
 
     
     
       13. The method of  claim 12 , wherein the receiving the phase modulation signal at a detector includes receiving the phase modulation information at a time-to-digital converter (TDC);
 wherein the method includes measuring phase differences between each phase modulation word of the phase data information and the phase modulation signal; and 
 wherein the determining the indication of nonlinearities includes determining the indication of nonlinearities using the phase differences. 
 
     
     
       14. The method of  claim 13 , wherein the receiving the phase modulation signal includes receiving the phase modulation information at a stochastic-beating TDC. 
     
     
       15. The method of  claim 12 , wherein the receiving the phase modulation signal a detector includes receiving the phase modulation information at a statistical extractor;
 wherein the method includes:
 statistically measuring the phase modulation signal using the statistical extractor; and 
 comparing the statistical measurement of the phase modulation signal to a known statistical measurement of the phase data information. 
 
 
     
     
       16. The method of  claim 15 , including adjusting parameters of a noise shaper of the DTC to compensate for nonlinearities of the DTC using the comparison of the statistical measurement of the phase modulation signal to the known statistical measurement of the phase data information. 
     
     
       17. The method of  claim 15 , wherein the determining an indication of nonlinearities of the DTC includes generating a pre-distortion mapping table comprising information to compensate for nonlinearities of the DTC using the comparison of the statistical measurement of the first modulation signal to the known statistical measurement of the phase data information. 
     
     
       18. The method of  claim 15 , wherein the statistically measuring the phase modulation signal includes generating a histogram of the phase modulation signal using a time-to-digital converter (TDC). 
     
     
       19. The method of  claim 15 , wherein the statistically measuring the phase modulation signal includes generating a histogram of the phase modulation signal using a stochastic-beating TDC. 
     
     
       20. The method of  claim 18 , including interpolating the histogram if the resolution of the DTC differs from the resolution of the TDC.